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Multi-Way Conventional loudspeakers with crossovers

Jeff Bagby's Tributes Build
Jeff Bagby's Tributes Build
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Old 3rd January 2017, 06:55 PM   #11
aeelements is offline aeelements  United States
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Default AR Series XO

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Originally Posted by rabbitz View Post
In post #5 I said I my try an AR series xo with these drivers and I've done just that. I'm not saying it's better than Jeff's excellent xo but is different in sonics and is more suitable for my use as well as I am working with different box volume and bass tuning. I won't go into any personal subjective impressions of the alternative AR series xo.

It drops the tweeter to 18dB down at the tweeter Fs, BSC is increased and the impedance plot is smoother and ranges from 9R to 5R45 from 100Hz which is better for my LM3886 based Arcam A19. Phase over the crossover is very good as can be seen in the reverse null FR.

I'm posting this for reference only for any future builders using these drivers and not to disrespect Jeff's excellent design. In fact the xo was designed using Jeff's SCD.
I'm interested in how you would describe the audible difference you hear between your XO and Jeff's original XO for the Tributes. I have grown to really like these two SB drivers together, but with my Tributes build, I feel the tweeter is far too bright on the top-end. I thought this would change with driver break-in, but they continued to be so bright I simply had to set them aside for the time being...
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Old 4th January 2017, 12:43 PM   #12
Zvu is offline Zvu  Serbia
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You should measure their frequency response and see if it looks all right.

Tributes don't have full BSC so that may be it. It depends on your preferences, amplifier and room too.
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Old 4th January 2017, 01:18 PM   #13
rabbitz is online now rabbitz  Australia
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I spent a few months living with the Tributes crossover and felt I could get more from the drivers as I've used SBA drivers before. The speaker sounded a bit restrained and needed more BSC. I did notice a edge or harshness to the sound on some female recordings (Katie Melua - Piece by piece for e.g.) that I use for speaker testing and I think that is due to the tweeter being only about 10dB down at Fs. I think the original Tributes specialise in mid presentation.

My box design is very different to JB's with a lower F3 and differences in shape, bracing and damping. The main differences in sonics of the AR series xo are: removal of edge / harshness; sound flows more freely; more body and fuller presentation; smoother overall sound; lower tweeter SPL. The xo I used has the tweeter Fs down 18dB, more BSC, tweeter has larger resistor, roll off on both drivers is smoother and the impedance curve is reasonably flat. All this makes a difference to the sound but this is subjective and to suit my tastes as my speakers are voiced to my "house sound" (presentation) that I prefer.

As I said before, I'm not knocking JBs design... I just took a different path that suits me.

Hope this helps aeelements.
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Old 4th January 2017, 01:24 PM   #14
rabbitz is online now rabbitz  Australia
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aeelements

You may want to check your xo wiring as it is a series xo and sequence of wiring is important. I didn't notice JBs xo as being too bright on the top end. I only noticed the tweeter Fs being pushed.

Also check your tweeter polarity. The other thing you can try is adding a 10R - 15R resistor parallel to the tweeter (from +ve to -ve terminal).

Should make no difference but my standard series xo's are wired a bit differently with the +ve input to the tweeter line (not the woofer). i.e. +ve in > 10uF > 3R > tweeter -ve > tweeter +ve > woofer +ve > woofer -ve > 0.8mH > -ve out. The parallel 0.8mH and 10uF remain the same. I've not seen it wired like JBs before with the +ve in to the woofer.
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Last edited by rabbitz; 4th January 2017 at 01:39 PM. Reason: xo details
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Old 4th January 2017, 03:15 PM   #15
aeelements is offline aeelements  United States
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Quote:
Originally Posted by rabbitz View Post
My box design is very different to JB's with a lower F3 and differences in shape, bracing and damping. The main differences in sonics of the AR series xo are: removal of edge / harshness; sound flows more freely; more body and fuller presentation; smoother overall sound; lower tweeter SPL. The xo I used has the tweeter Fs down 18dB, more BSC, tweeter has larger resistor, roll off on both drivers is smoother and the impedance curve is reasonably flat. All this makes a difference to the sound but this is subjective and to suit my tastes as my speakers are voiced to my "house sound" (presentation) that I prefer.
Hope this helps aeelements.
Firstly, I appreciate all of this thoughtful information. It's good to know I'm not simply "left hanging" in this wild world of DIY.

I'm very interested in your version of the xo for this design. I'm wondering if it would work without modifying my cabinets too much... I basically built the Tributes with a typical 15 liter cabinet using birch ply, complete with half-inch rounds, internal bracing and a rear 2" by 8" port, tuned to 38 Hz. After all of this work I'd really like to use these cabinets as they turned out quite nice!

I'm extremely interested in a smoother and fuller representation. I can sort of feel these drivers are cable of doing so. As to why my tweeters sound super-hot, maybe they should be weird with the positive side to the tweeters rather than the woofers... Or perhaps I should try that extra resistor in parallel to the tweeter. They're so hot, in fact, that the sound (while clean) is thinned. I have had to use tone controls to attenuate the highs far beyond what I've ever experienced and even add some bottom end to help fill-in the sound. Albeit this is a bedroom with lower ceilings, but I've auditioned many a speaker in this listening environment and these are way out there. I have them next to a pair of Mandolins (also by Jeff Bagby) and the sound is entirely different (brighter, sparkling highs which sound impressive at first, but are far too overpowering) in the top half of the spectrum. The bottom half sounds quite similar to the Mandolins. I expected them to with an almost twin driver and cabinet size.

Thank you, again, for sharing your perspectives and thoughts. I'm excited to see where this can go!
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Old 5th January 2017, 12:51 PM   #16
rabbitz is online now rabbitz  Australia
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The AR series xo would be fine in the Tributes box as the effective baffle width is the same but you can do some changes to the existing speaker.

Your use of the tone control to lower the top and increase the bass does point to some things you can try.

1. Check your wiring and driver polarity.
2. Add the 15R resistor parallel to the tweeter as will attenuate the tweeter without upsetting the filter, phase etc. It also has the added benefit of helping with a bit more BSC and driving the tweeter lower at Fs plus the roll off is smoother (see graphs for tweeter without and with 15R). If you need more, then use a 10R.
3. I still feel the port is too long with the Fb too low. I tuned my 18L to 43Hz (51x146 port), and Troels tuned his 16L to 45Hz (50x145 port in the parts list).
SBAcoustics-61-MFC
For a smallish box, a 2dB hump in the bass adds more body and enjoyment to the sound IMO.
For a 15L box, I'd try a port 51x165.
4. If you have the box stuffed as per the Tribute write up, I'd change the damping so it has a layer over the back and bottom with some 6mm felt on the sides. This generally works well in vented designs.
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A small quasi-TL is going to help the mids more than the lower end. See Troels above as has a link to his damping.

You could always try the xo from your other speaker but the tweeter padding would have to be reduced (lower tweeter SPL) and may effect the overall result.
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File Type: jpg Tribute_tweeter.JPG (50.4 KB, 529 views)
File Type: jpg Tribute_tweeter_15R.JPG (49.3 KB, 519 views)
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Last edited by rabbitz; 5th January 2017 at 12:55 PM.
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Old 10th January 2017, 02:30 PM   #17
aeelements is offline aeelements  United States
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Thanks for sharing all of this! I've spent the weekend soldering and listening.

1. The wiring for the original Tributes crossover looks to be proper when comparing to Jeff's document (with the - to the woofer, not as you've mentioned with the + to the woofer). I have not tried it that way... yet.
2. I went straight to adding a 10R resistor in parallel to the tweeter and wow, now things are starting to come together. I still feel things are a tad on the bright side, but things are sounding quite workable. I wonder if the current drivers have different sensitivities when compared to the ones Jeff used when voicing the Tributes?
3. I have no messed with the port dimensions as of yet, since I've been so focused on getting the top-end correct, but will look into that if I must.
4. I may want to mess with internal dampening as certain bass notes can become louder than others. This could also be room-induced.

When you say a quasi-TL is going to help the mids more than the lower end, do you mean when compared to traditional designs?

I have both the Tributes and the Mandolins side-by-side for comparison. While the bottom-end sounds similar between the two, the midrange is far more pronounced and focused on the Mandolins, yet with an almost restricted/compressed sounding very top-end. The Tributes' top-end is far more pronounced, with a greater sense of height, air and space, with a less compressed sound and a more relaxed, smoother (albeit less pronounced) midrange. Interesting... (Mandolin crossovers came pre-assembled)

I've always loved the beautiful midrange and fullness of weight from the Mandolins (been listening for years) but have always felt the top-end was restrained which, to me, made the representation compressed sounding (harsh in the 4-6k region. could be room reflections due to a very flat sound).

This is why I went for the Tributes, with the hopes of capturing some of what the Mandolins produced, with a more open top-end so the sound could breathe a little and become a bit more transparent.

Your advice has helped, primarily by adding that 10R resistor to the tweeter. I wonder if I could attenuate just a bit more, even....

I also need to find a way to take measurements so others can see what I'm describing.
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Old 11th January 2017, 12:37 PM   #18
rabbitz is online now rabbitz  Australia
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Jeff's schematic I have has +ve to the woofer so there may have been some confusion in my alternate description. I've add his schematic (yours may be different) with polarity changes I was on about.

Glad the 10R parallel resistor helped. If you want to attenuate the tweeter a little more, change the 3R to 3R9 which doesn't upset the filter characteristics (could go as high as 4R7 only if absolutely necessary). Any cap or inductor changes would be detrimental to the design goals. I have never noticed SB Acoustic drivers having great variations (very well made).

Bass notes are very room dependant and distances to boundaries such as back and side walls. Moving the speaker around can make a huge difference, even to mids, and keep distances to boundaries different and not direct multiples of each other. Toeing out or not toeing in of the speakers can help a hot top end. Moving speakers further out from the wall gives the impression of cleaner and more mids.

Interesting comment on the top end of the Mandolin which uses a ring dome. Some like them and others don't. I've never heard it but have never liked the Vifa XT25TG ring radiator but others love it. I imagine the Mandolin is a standard rear vented bass reflex with minimal internal damping which maybe is one of the reasons for the more pronounced mids. You can try the same damping arrangement on the Tribute as full box damping can effect the overall presence of the mids and suck some life out of it.

A small TL design generally has better mids than a bass reflex speaker but would be the other way around with bass performance on a small speaker like the Tribute.

I'd try the resistor change as well as changing the damping arrangement which I think should get you closer to where you want to be (plus moving them in the room).
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Old 31st January 2017, 12:09 PM   #19
Cambe is offline Cambe
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Rabbitz,
I sent you a PM.
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Old 1st February 2017, 03:50 AM   #20
rabbitz is online now rabbitz  Australia
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PM received.
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